Some things just don’t belong or make any sense

What on earth is the purpose of the Oozes/Puddings? I just cannot figure out what they exist for, or how they would fit in any ecosystem, even one as odd as the standard D&D one. Sure there are some strange thigns out there, strange plant creatures, Monster earth burrowers. But the Oozes just don’t make any sense.

Of course I will admit that I don’t exactly run a lot of traditional Dungeon Crawls. That would be because the idea of a bunch of underground fortresses don’t make a lot of sense to me either. I guess I run different kind of campaign than that. Maybe if the group was underground more, delving into tunnels and fortresses it might make more sense that there was somehow a creature made of ooze. But I don’t, and therefore this just doesn’t make sense to me.